Massdrop x Eddie Current ZDT Jr. (Official Thread)

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Hands, Nov 15, 2017.

  1. David De Lucena

    David De Lucena Science Nut

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    Did you had the time to compare the zdj vs amethyst headphone output?
     
  2. PrismaticOrb

    PrismaticOrb Rando

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    Could you direct me to a link of the correct ge 5654w tubes. I just bought four that turned out to be sylvania jan 5654w tubes from a seller on ebay who told me I bought the wrong tubes after inquiry and proceeded to send them to me anyway. Much appreciated!
     
  3. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I mean...Just look on eBay for the GE 5654 tubes. Green lettering, often come in packs of 4+ in fairly plain, white boxes.

    Though I don't see why the Sylvanias wont work if they too are 5654. Worth a shot. They might sound good!
     
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  4. Ringingears

    Ringingears Honorary BFF

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  5. PrismaticOrb

    PrismaticOrb Rando

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    Thank you so much!
     
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  6. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Just for the hell of it, I turned the power off on my NBM while music was still playing. It slowly faded out, with the channel balance shifting back and forth from left to right. Is this due to the heaters in the tubes slowly cooling down? I would have thought that the drop off would have been more abrupt, but maybe this is the nature of a "pure" tube amp.
     
  7. PrismaticOrb

    PrismaticOrb Rando

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    Noticing a faint hum in the background on this unit. Low enough you can't tell when music is playing but it is definitely there. Wondering how loud the hum is on the older units?
     
  8. Ringingears

    Ringingears Honorary BFF

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    Pretty sure it’s normal. My BAT VK-60 power amp does the same on my speaker set up.
     
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  9. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I didn't think it was abnormal, just wondered about the physics behind it. I'm used to amps going silent with a slight "thunk" when powered off, due to a relay disconnecting I would guess.

    After swapping tubes, I powered it back on with the musics playing and the volume ramped up gradually, though faster on the one side than the other. I guess with transformer coupling on both inputs and outputs, there's no need for any power up/down safety electronics.

    That is a beautiful looking piece of kit!
    https://www.stereophile.com/tubepreamps/766/index.html
     
  10. Ksaurav402

    Ksaurav402 Acquaintance

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    I have got the newer one. Although its faint but its definitely there. However not that noticeable.
    I feel it is more out of my HD600 then verite
     
  11. Ringingears

    Ringingears Honorary BFF

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    Funny thing is I ended pairing them, I have the VK-3i pre, with the Dunlavy SC-IVa’s a latter and better version of the SC-IV. Never read the article until later.
     
  12. PrismaticOrb

    PrismaticOrb Rando

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    I mentioned it to drop, they dispatched a new one without batting an eye. I sort of feel bad as I'm pretty sure the one they send out will have the same issue. Seems like it would be a better business practice to enforce more strict qc than pay for it on the back end with shipping and handeling. But what do I know.
     
  13. Tom2502

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    I would also say that this is normal. Wenn I turn off various guitar tube amplifiers they do the same thing. Slowly the output fades, an amp that I have in mind slightly distorts the output while doing it (an old modified stereo amp from 1960/61). I guess that it is related to capacitors and other parts that act as buffer still operate while they have sufficient charge.
    I would like a detailed technical explanation too, I'm sure there are a bunch of people here that could explain way better what's happening inside :)
     
  14. Ksaurav402

    Ksaurav402 Acquaintance

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    Do let us know if the new one has same issue or if it is dead silent.
     
  15. Zampotech

    Zampotech Friend

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    Perhaps you're worrying in vain. Probably your amplifier will be subject to additional measurement or return to the supplier as defective.
    This is a normal, standard process.
     
  16. PrismaticOrb

    PrismaticOrb Rando

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    Well update on that.. that amp randomly popped twice in the right channel. Not sure if it is the tubes or what but it hasn't been moved around or anything since it's been plugged in. Those pops not only made my right ear ring for a while but I'm pretty sure it damaged the driver in the hd6xx. I'm getting some nice new distortion in certain bass ranges. A little pissed. I have had nothing but problems with the amps and now the one item that had no problems is not performing right. Still have to wait another week for the replacement to arrive bit not even sure at this point if I want to plug my other set of headphones into the new amp to have the same thing happen to a pair twice as expensive.
     
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  17. Zampotech

    Zampotech Friend

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    Very interesting and mysterious defect.
    Popped can OTL amplifier, if output capacitor is destroyed. But this is fundamentally not typical for the SET amplifier.

    If the right driver of the earphone is still damaged, it means that the output has a large constant voltage. In NBM (and possibly ZDT-Jr), none of the output wires have a galvanic connection to the amplifier. The magnetic connection only, through the transformer. The output voltage can occur a maximum of 6 volts AC voltage only. The output transformer is not physically capable of higher voltage.This connection is not enough to mechanically damage the earphone. It adds to the mystery...

    It would be interesting to know the fate of this unfortunate amplifier.
     
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  18. PrismaticOrb

    PrismaticOrb Rando

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    I'm just stating what happened. Not trying to smear the amps name. I've been using tube amps my whole life. Even professional hand wired amps up to 8x the price. Im not sure what it is you are eluding to. It's not a mystery to me just simply what happened. Maybe shoddy manufacturing of a mass produced product...or a defective component or tube. It pushed the driver in the headphone. But that's all the input i have or care to receive. Take down my posts if it doesn't gel with the vibe you guys are aiming for in this thread. It is my own personal experience with "this" product.
     
    Last edited: Jul 28, 2019
  19. Zampotech

    Zampotech Friend

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    I'm also very interested in what happened. I have never in my repair practice encountered such a defect. I am engaged in repair and this defect is interesting to me in the academic plan.

    It would be great if MASSDROP repairmen published their findings. Can you ask them to do that?
     
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  20. gixxerwimp

    gixxerwimp Professional tricycle rider

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    @Zampotech is highly familiar with the design of this amp and all he's doing is explaining why it's very strange that yours would have damaged the driver of your HD6xx in the way you described. Don't read anything else into it. If you have any more info to share about your issue, people here are interested to read about it.
     
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